Your Guide to Prenatal Tests

Throughout even the healthiest, low-risk pregnancy, an expectant mama is likely to undergo a full battery of tests, in part simply because it’s possible nowadays (and useful) to find out quite a bit more about the health of our babies than when our moms were pregnant with us. While some tests monitor your health, others check that of your baby. Many, if not most, are routine, while others are optional and more relevant to specific populations.

Before you read any further, you should know that there are two types of genetic tests: screening and diagnostic tests. A screening test assesses your particular risk of having a baby with a certain birth defect, e.g. a 1 in 400 chance or 1 in 2,300, while a diagnostic test gives you a near-definitive answer as to whether your baby has a particular birth defect. Depending on the results of your screening tests, your healthcare provider may recommend follow-up diagnostic testing.

Your healthcare provider can tell you which tests pertain to your specific pregnancy, given your past and current medical history, but we checked in with Michele Hakakha, M.D., an ob-gyn in private practice in Beverly Hills, CA and co-author of Expecting 411: Clear Answers & Smart Advice for Your Pregnancy to offer you a trimester-by-trimester guide to the tests a modern mama-to-be is likely to face, along with any risks associated with the tests, and what to do if there’s a problem.

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Complete Blood Count

Who: All women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

Results and follow-up: If you're slightly anemic, your doctor will likely instruct you to eat more iron-rich foods—lean meats, green leafy veggies, beans, and lentils. If you need more iron than you can squeeze into your diet, your doctor may recommend a daily iron supplement in addition to your prenatal vitamin. Certain types of anemia can be a red flag for inherited blood disorders such as sickle cell disease that could potentially be passed onto baby; your doctor may order more tests. And if your white blood cell count comes in high, or your platelet count low, you may also need further testing to determine the best course of action, if any.

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Blood Type & Rh/Antibody Screen

Who: All women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: A blood test

Why: To determine your blood type and Rh status. Your baby’s pediatrician will eventually need this information, because if you have type “O” blood and deliver a baby with “A” or “B” blood type, he may be at greater risk for jaundice. It’s also helpful data for your healthcare provider, in case you have complications during labor and need a transfusion. Secondly, the Rh factor is a protein found on red blood cells. If you are Rh-negative (meaning that you don’t have the protein) and your fetus is Rh-positive, your body may produce antibodies that attack your baby's red blood cells, potentially causing him to develop severe anemia in utero.

Results & follow-up: If an Rh difference is detected, a doctor can provide injections of Rh immune globulin to prevent this type of reaction (usually at 28 weeks gestation and within 72 hours of giving birth, although a dose may also be given if a woman has a miscarriage, bleeding, or an amniocentesis or other invasive testing during pregnancy).

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Rubella Immunity

Who: Most women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: A blood test

Why: To detect antibodies to rubella (German measles), which indicate immunity to the disease. You likely received the MMR vaccine at some point in your life, but immunity may have worn off, so ideally this is something doctors like to check for during a preconception visit. That way, if you’re not immune, you can be vaccinated (and should wait three months following vaccination to conceive). If antibodies are not present in a pregnant woman, exposure to the disease could cause birth defects, blindness, deafness, preterm birth, miscarriage or stillbirth, among other problems.

Results and follow-up: The vast majority of women in the U.S. are immune, thanks to a major vaccination effort, but if you’re not, you should make sure that your kids, if you have any others at home, have had all of their shots and that anyone else at home who’s not immune gets vaccinated. If there’s even a single known case of rubella in your community, you should stay home until it’s confirmed that the danger of infection has passed. Sounds drastic, but if you contract rubella during the first 12 weeks, there’s up to an 85 percent chance that your baby will develop congenital rubella syndrome (CRS), which can cause deafness, eye defects, and major neurologic problems. After 20 weeks of pregnancy, thankfully, there’s little risk that a rubella infection would cause any birth defects.

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Varicella Immunity

Who: Most women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: A blood test

Why: To detect antibodies to the chickenpox virus (varicella), which indicate immunity to the disease. The good news is that more than 90 percent of pregnant women are immune because they either had chickenpox earlier or were vaccinated as kids, but immunity can decrease over time. Chickenpox in pregnancy can cause congenital varicella syndrome, a group of birth defects that can include blindness, seizures, neurological problems, and malformed and paralyzed limbs. Fortunately, varicella syndrome affects just one to two percent of babies whose moms were infected in the first half of pregnancy—and birth defects are very rare when infection occurs in the latter half of pregnancy.

Results and follow-up: If you’re not immune to chickenpox, you should avoid anyone with chickenpox or shingles during your pregnancy. If you have been exposed to someone with chickenpox, see your healthcare provider within 96 hours (four days) for treatment with VariZIG, which can prevent the illness or lessen its severity. Should you come down with chickenpox during pregnancy, your healthcare provider will likely treat you with the oral antiviral drug acyclovir (which is believed to be safe during pregnancy) to help ease symptoms.

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Hepatitis B

Who: All women

When: Can be done anytime during pregnancy, but usually at your first prenatal visit

How: A blood test

Why: To check for the hepatitis B virus (HBV), which can cause severe illness, liver damage, and even death—and can be passed to the baby at birth. According to the World Health Organization, about a quarter of the world’s population have been infected with HBV, but many of them have no symptoms and are unaware that they’re carriers of the virus.

Results and follow-up: The test for hepatitis B will tell your doctor one of three things: if you have been vaccinated against HBV, if you were infected with HBV in the past but no longer have the virus, or if you are a chronic carrier of HBV. Should the test reveal that you are a chronic carrier, you should consult with a perinatologist (a specialist who deals with high-risk pregnancies) and an infectious disease specialist in addition to your midwife or OB; it’s important to monitor your liver function. Your baby should receive a shot of hepatitis B antibodies as well as his first dose of the hepatitis B vaccine at birth (second and third doses should be given at regular doctor’s visits; all three are necessary for protection).

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Syphilis

Who: All women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: A blood test

Why: As with many other STDs, women can be infected without knowing it (although men who are infected may have a syphilis sore called a chancre on their penis, women may have vaginal or rectal sores that aren’t painful or visible). If left untreated during pregnancy, syphilis can lead to miscarriage or stillbirth, and a pregnant mom can pass syphilis to her baby through the placenta or during delivery, possibly leading to blindness, deafness, and bone deformities in her baby.

Results & follow-up: If you test positive for syphilis, your healthcare provider will prescribe a course of antibiotics considered safe for pregnancy.

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Chlamydia/Gonorrhea

Who: All women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: Swabs of the cervix

Why: To test for sexually transmitted diseases (STDs) which, if left untreated, can cause pelvic infections that can lead to miscarriage, pelvic inflammatory disease, premature rupture of membranes (when your water breaks early), and preterm labor. Babies born to actively infected moms are at risk for eye infections, blindness, and pneumonia.

Results & follow-up: If you test positive for gonorrhea or chlamydia, you'll be treated with antibiotics that are safe for your fetus. You should not resume sexual relations with a partner who has not been tested and treated as well.

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HIV

Who: All women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: A blood test

Why: The human immunodeficiency virus (HIV), the virus that causes AIDS, can cross the placenta before or during delivery and infect the fetus.

Results & follow-up: If you're an HIV carrier, you'll be given medication during pregnancy and delivery that decreases the risk of mother-to-baby transmission from 25 percent to about two percent or less, according to the CDC. If you are HIV-positive, you’ll also need to see a perinatologist and an infectious disease specialist, in addition to your obstetrician or midwife. Women known to be at high risk for becoming infected—drug users and their partners, women who exchange sex for money or drugs, women with new or more than one sex partner during pregnancy, and women who are sexual partners of HIV-infected people—will likely be re-tested in the third trimester.

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Pap Smear

Who: All women

When: At your first prenatal visit (generally six to ten weeks into your pregnancy)

How: A swab of cells from your cervix

Why: To detect cervical cancer

Results and follow-up: If you have an abnormal Pap result, next steps may include a colposcopy, which uses a special kind of microscope to look at cells on the cervix. If precancerous or cancerous growth is revealed, which is relatively rare, treatment will begin during or after pregnancy, depending on how advanced the cancer is.

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Blood Pressure

Who: All women

When: At each prenatal visit

How: The standard armband test

Why: Although it’s protocol at any doctor’s visit, whether or not you’re pregnant, checking your blood pressure now is especially important because pregnancy can cause high blood pressure. In particular, your healthcare provider will be on the lookout for gestational hypertension and preeclampsia.

Results and follow-up: A spike, along with protein in your urine, may indicate preeclampsia (high blood pressure during pregnancy). The condition, which affects between five and eight percent of pregnant women, can keep your baby from gaining weight properly, cause the placenta to separate from the wall of the uterus, and put you at risk for a stroke, liver dysfunction, and other problems. Mild cases can be treated with bed rest; severe ones may require antihypertensive drugs or an early delivery.

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Urine Tests

Who: All women

When: At each prenatal visit

How: Peeing in a cup

Why: A pregnant gal’s pee actually tells quite a bit about the state of her health. Not only do urine tests help detect bladder infections (which can be asymptomatic during pregnancy—and risk leading to a kidney infection and preterm labor). Your doc will check for protein (a possible sign of preeclampsia; see previous slide), sugar (too much may signal gestational diabetes), and, in some cases, for blood and bacteria (which could indicate a urinary tract infection).

Results and follow-up: Gestational diabetes, which can make your baby grow too quickly, rarely develops until the second or third trimester. Milder cases may be controlled with diet, and in more severe cases, insulin. A urinary-tract infection can be cured with baby-safe antibiotics (untreated, it can lead to a kidney infection and preterm labor).

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Cytomegalovirus (CMV)

Who: Women who work with the very young (in a daycare center, for example), the elderly, or AIDS patients.

When: Possibly during the first prenatal visit for women who fall into the higher risk categories above, although some doctors may diagnose CMV infection following the discovery of something unusual in the second trimester ultrasound. The diagnosis can be confirmed through amniocentesis.

How: A blood test

Why: CMV is a herpes virus that is contracted through sexual relations or through infected blood, urine, or saliva. It can be transmitted to the baby in utero and cause serious problems such as hearing loss, blindness, seizures, neurological disorders, a small head (microcephaly), and stillbirth. If a woman becomes infected during pregnancy, her baby has a 30 to 40 percent chance of becoming infected.

Results and follow-up: If your blood work indicates that you have already been exposed to CMV, rest easy; you can’t be infected again and your baby isn’t at risk. If you are not immune to CMV, however, you should take precautions to protect you and your baby, including wearing gloves when handling dirty diapers or dealing with immune-compromised individuals (e.g., the elderly or AIDS patients) and washing your hands often.

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Parvovirus

Who: Women exposed to the virus—generally through a young child—including moms, early childhood educators, and pediatricians.

When: At any time

How: A blood test

Why: Also known as fifth disease or “slapped cheek” disease (because kids develop red cheeks one to two weeks after they were contagious), parvovirus can potentially cause fetal anemia. The greatest risk to your baby is if you are exposed before 20 weeks gestation, but tell your doctor if you think you might have been exposed to it at any time. Fortunately, most adults are immune because they’ve had the virus as kids.

Results and follow-up: If you do contract parvovirus, your doctor will monitor your baby via regular ultrasounds to confirm that he’s not becoming anemic, a very rare result of this infection. Amniocentesis can also check for fetal infection. Rest assured that in most cases, babies of moms who got parvovirus while pregnant turn out just fine.

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Ultrasound

Who: Most women

When: Usually at least once in the first trimester and again around 18 to 20 weeks

How: A handheld device called a transducer is placed on the abdomen (or in the vagina, in the case of an ultrasound before about 12 weeks of pregnancy). Sound waves from the transducer create pictures of the fetus on a monitor and pick up the sounds of the fetal heartbeat.

Why: Because you want a peek at the cutie in your tummy! From your doctor’s perspective, though, ultrasounds are done to establish a due date, confirm that the fetus is in the uterus (and not in a fallopian tube, as in the case of an ectopic pregnancy), monitor fetal growth, and to check for multiple fetuses. Later ultrasounds (around 20 weeks) look at all of your baby’s internal and external structures, the placement of the placenta, the amount of amniotic fluid in the uterus, and can usually reveal the baby’s sex. An ultrasound at this time can also reveal some birth defects, such as a heart defect, cleft palate, or spina bifida (an opening in the spine).

Results and follow-up: Follow-up depends on the reason for the ultrasound. If your doctor was trying to determine the fetus's age, your due date may be adjusted. If she suspects a growth abnormality, you have the option of further testing to verify the diagnosis.

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Cystic Fibrosis (CF)

Who: The American Congress of Obstetricians and Gynecologists (ACOG) now recommends that everyone be offered the screening test, though Caucasians and Ashkenazi Jews, or women have CF in their family background, are at the highest risk for being CF carriers.

When: During the first or second trimester, ideally before 20 weeks, or during preconception counseling

How: A blood test determines whether one or both parents are carriers of CF

Why: If both parents are carriers, there is a one in four chance that their baby will have CF, a lung disease that causes life-threatening lung infections and serious digestive problems.

Results and follow-up: If a pregnant woman tests positive and is found to be a carrier of cystic fibrosis, her partner should then be tested. If both parents are CF carriers, doctors can test the fetus for CF through chorionic villus sampling (CVS) or amniocentesis.

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Ashkenazi Jewish Genetic Panel (AJGP)

Who: Ashkenazi Jewish women having a baby with an Ashkenazi Jewish man. Some doctors may recommend getting the panel done even if only one partner is Jewish, although the risk of a child with only one Ashkenazi Jewish parent having these diseases is far less.

When: During the first or second trimester, ideally before 20 weeks

How: A blood test

Why: To detect a variety of different genetic disorders common within this ethnic group, including Tay Sachs, Maple Syrup Urine Disease, Canavan’s Disease, and cystic fibrosis (since the risk of being a CF carrier is higher in Ashkenazi Jews)

Results and follow-up: If a pregnant woman tests positive and is found to be a carrier, her partner should then be tested. If both parents are carriers, there is a one in four chance that their baby will have one of these diseases. The baby can be tested through chorionic villus sampling (CVS) or amniocentesis.

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Thalassemia Screen

Who: Women of Italian, Greek, Middle Eastern, Asian, and African ancestry, or women who have a known family history of thalassemia

When: During the first or second trimester, ideally before 20 weeks

How: A blood test

Why: Thalassemia is a genetically inherited blood disorder that causes the body to make an abnormal amount of hemoglobin, resulting in excessive destruction of red blood cells which, in turn, leads to anemia. It’s among the most common genetic disorders worldwide. A routine complete blood count identifies those at risk for being a carrier. If you’re anemic and have smaller-than-average red blood cells, your healthcare provider can order additional testing called a hemoglobin electrophoresis, which will help to detect thalassemia (as well as other blood disorders, including sickle cell anemia).

Results and follow-up: If you test positive as a carrier of abnormal thalassemia genes, your partner should be tested. If both parents are carriers, your healthcare provider may suggest additional prenatal testing such as chorionic villus sampling (CVS) or amniocentesis to see if your baby has it as well. The most severe form of alpha thalassemia major causes stillbirth. Children born with thalassemia major (Cooley’s anemia) are normal at birth but develop severe anemia during the first year of life. Treatment for thalassemia major often involves regular blood transfusions and folate supplements.

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Sickle Cell Screen

Who: Women of African or Mediterranean ancestry, who are at greater risk for having or carrying the trait for sickle cell anemia

When: During the first or second trimester, ideally before 20 weeks

How: A blood test

Why: Sickle cell disease, a genetically inherited blood disorder, causes sickle-shaped (instead of round) red blood cells that obstruct capillaries and may lead to severe anemia, pain, and lack of blood flow to some organs

Results and follow-up: In pregnancy, sickle-cell anemia can lead to complications including intrauterine growth retardation, spontaneous abortion, and preeclampsia; your healthcare provider will want to monitor you carefully. It’s only possible for your baby to get sickle cell disease if both parents have the sickle cell trait. If so, chorionic villus sampling (CVS) or amniocentesis can be done to determine if the baby has the disease or carries the trait.

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"I Didn't Even Know I Was Pregnant!"On the morning before the Fourth of July, Jennifer West woke up to severe stomach and back pain. What was supposed to be a relaxing vacation with friends and family became a painful and uncomfortable day in bed. As the pain deepened, West’s husband was overwhelmed with concern and persuaded his wife to go to the hospital. It was there in the waiting room that 31-year-old Dan West learned he was going to be a father and fast. Jennifer had still been having monthly periods, and was stunned by the news. However, after a few hours in labor, Robert Hayward West was born healthy, at eight pounds even.

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First Trimester Screening

Who: Available to all women

When: Between 10 and 14 weeks, although usually between 11 and 13 weeks

How: This screening has two parts: a blood test to measure levels of two pregnancy-specific hormones (beta hCG and PAPP-A) and an ultrasound exam to measure the fluid beneath the skin at the back of the fetus’ neck (nuchal translucency). Using your age and the results from those tests, your healthcare provider can assess your personal and immediate risk of carrying a baby with specific chromosomal abnormalities, which will be given to you as a risk of, say, 1 in 800 or 1 in 4,000.

Why: To screen for trisomy 21 (Down syndrome, which causes mental retardation) and trisomy 18 (Edwards syndrome, which causes more severe retardation and is often fatal by age 1), and sometimes trisomy 13 (Patau syndrome, which often causes congenital heart disease) earlier than standard second-trimester testing. It does not evaluate the risk of neural tube defects such as spina bifida.

Results and follow-up: If your results show a high risk of an abnormality, your doctor may recommend further testing, such as a chorionic villus sampling (CVS) or amniocentesis, to confirm the diagnosis. But don’t panic—your results only indicate a possible risk. Most likely, your baby is fine.

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Chorionic Villus Sampling (CVS)

Who: Women over 35 and those who have—or whose partners have—a family history of genetic diseases such as cystic fibrosis

When: Between 10 and 13 weeks

How: Using ultrasound as a guide, a doctor inserts a catheter through the cervix or a needle into the abdomen to retrieve sample cells from within the chorionic villi, which are tiny parts of the placenta.

Why:To test for genetic disorders such as Down syndrome, sickle cell anemia, and cystic fibrosis.

Results and follow-up: The results, which are more than 99 percent accurate, are generally available within seven to ten days. A faster test, known as "FISH" (fluorescent in situ hybridization), can quickly check for five major chromosomal abnormalities, including Down syndrome; this test gives results in two or three days. The main advantage of CVS is that it can be done early in the pregnancy, but it does carry a (roughly) one in 400 risk of miscarriage (the same risk as for amniocentesis). Additionally, you’ll need to be on bedrest for 24 to 48 hours after the procedure with activity restrictions for a week.

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Expanded AFP Test (Triple Screen)

Who: Available to all women

When: Between 15 and 20 weeks, although safest between 16 and 18 weeks

How: A blood test

Why: This test checks for genetic abnormalities such as trisomies 18 and 21, neural tube defects (such as spina bifida), major brain defects (anencephaly) and abdominal wall defects (such as gastroschisis and omphalocele), as well as Smith-Lemli-Opitz Syndrome (a rare developmental disorder that affects many parts of the body and is characterized by small head size, intellectual disability, and behavioral problems). It measures the level of a protein produced by the fetus called alpha-fetoprotein (AFP) as well as that of two hormones, human chorionic gonadotropin (hCG) and estriol.

Results and follow-up: Results are available within one to two weeks. If your levels of AFP and estriol are low and the level of hCG is high, your baby has an increased risk of Down syndrome. A high reading of AFP may signify a neural tube defect. If your results are abnormal, you'll be offered an amniocentesis. Note: These tests have a high false-positive rate: 50 out of every 1,000 women will be told that their fetus is at risk; of these, only one or two babies will actually have Down syndrome.

Note: Although the triple screen is the most common test, there are three newer versions of it that your doctor may order instead: The quadruple screen, serum integrated screening, and full integrated screening.

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Amniocentesis

Who: Women over 35, those who have—or whose partners have—a family history of genetic diseases, and those whose triple screen test results are abnormal

When: At 15 to 20 weeks

How: Guided by ultrasound, a doctor inserts a needle into the abdomen to draw a sample of amniotic fluid. Most women report it’s not as uncomfortable as it sounds.

Why: An amnio detects neural tube defects, Down syndrome, and other genetic disorders such as cystic fibrosis and thalassemia.

Results and follow-up: The test is 99 percent accurate; results are available in seven to ten days. A faster test, known as "FISH" (fluorescent in situ hybridization), can return results sooner, in two or three days. The miscarriage rate for the procedure is about one in 400.

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Glucose Test

Who: All women

When: Usually between 24 and 28 weeks, though women at greater risk for gestational diabetes (including those with a history of gestational diabetes, a family history of diabetes, women over 35 and those who are obese) may have it done as early as the first prenatal visit.

How: A blood test after you drink eight ounces of a sugary liquid (glucola) within about five minutes.

Results and follow-up: If levels are high, a second, longer test (the three-hour glucose tolerance test; see next slide) can more accurately diagnose the condition.

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3-Hour Glucose Tolerance Test

Who: Women who received abnormal results from their glucose test

When: Following overly high results from the glucose test

How: For starters, you’ll need to consume at least 150 grams of carbohydrates per day (which probably means you’ll have to polish off an extra piece of bread at each meal, but ask your doctor for specifics on what you should eat) for at least three days before the test. Then you’ll fast for eight to fourteen hours (only sips of water allowed) before getting your blood drawn. Afterwards, you’ll be asked to drink another glucose beverage with double the sugar of the one from your first glucose test (yuck!). Finally, your blood will be drawn every hour for three hours. It’s a looong day.

Why: To confirm whether you actually have gestational diabetes.

Results and follow-up: Gestational diabetes can be controlled with diet and, in some cases, insulin. But, you’ll need to learn how to check your own blood sugars (by pricking your finger a few times a day).

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Fetal Kick Counts

Who: All women

When: Usually starting around 26 weeks

How: Easy: Pay attention to how often your little Pele kicks your ribs. Some doctors ask that you sit for an hour and count how many times your baby moves in that period, while others just want you to confirm that you’re feeling some movement every 12 hours or so.

Why: To confirm that your baby is healthy and active in there.

Results and follow-up: If you don’t feel much movement, try to eat or drink something (sugary stuff works best), and lie on your left side. If you still don’t feel much in the next hour or so, call your healthcare provider right away. While your baby may simply be sleeping, your doctor will want to make sure that there’s not another reason for little or no movement, such as low levels of amniotic fluid or insufficient oxygen.

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Non-stress Test

Who: Women who have high-risk pregnancies (including preeclampsia or diabetes), who have had problems with previous pregnancies, who are carrying multiples, or who have noticed a drop in their baby’s movement

When: Anytime in the last trimester, generally done on a weekly basis (or even twice weekly in very high-risk pregnancies)

How: Two monitors are strapped to your abdomen, one to measure uterine contractions and the other to measure your baby’s heartbeat.

Why: To monitor the fetal heart rate

Results and follow-up: The fetal heart rate usually quickens in response to stimuli, such as noise. If your baby’s heart rate doesn't change, you may be given the test again or take further tests, such as a biophysical profile.

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Biophysical Profile

Who: Women whose doctors have a concern about the fetus's wellbeing

When: Anytime during the third trimester

How: An ultrasound combined with a non-stress test

Why: To measure the amniotic fluid and the baby's muscle tone, "breathing" movements, and activity level.

Results and follow-up: You’ll get scored for this test, on a scale of 0 to 10, which helps your doctor to determine whether more testing—or immediate intervention—is needed. If a problem such as low amniotic fluid is found, the baby may need to be delivered early.

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Group B Strep (GBS)

Who: Most women

When: Between 35 and 37 weeks; women undergoing a chorionic villus sampling ( CVS) in the first trimester will also need a Group B Strep test before the procedure

How: Cells are swabbed from the rectum and vagina

Why: Group B streptococcus (GBS) bacteria is carried by 10 to 30 percent of all pregnant women, and it can be transmitted to your baby during vaginal delivery, possibly causing meningitis or even death. Some doctors only screen women considered at risk—women with a history of urinary tract infections, a fever near delivery time, or who have delivered a previous baby with GBS. Ask to be tested even if you don’t fall into any of those at-risk groups.

Results and follow-up: If you test positive, you'll receive antibiotics during delivery to help prevent perinatal transmission. (If you have a c-section, you won’t need the antibiotics, as your baby won’t be going through the birth canal.) It’s standard protocol for your newborn to get a complete blood count and blood culture if you are GBS positive and didn’t get pre-treated with at least one dose of antibiotics (which could happen if your labor goes really fast), or if your baby was born prior to 35 weeks. If the bacteria is passed to your baby, GBS can usually be treated successfully with antibiotics.

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Fetal Fibronectin (fFN)

Who: Women at risk of going into preterm labor

When: Between 22 and 34 weeks

How: A swab of fluid from the back of the vagina. Sometimes a vaginal ultrasound is done after the sample is taken to measure cervical length, which often decreases before labor begins

Why: To check for the presence of fetal fibronectin which is basically the glue attaching the amniotic sac to the inner lining of the uterus

Results and follow-up: Results are usually available within one to two hours. A positive result means that fFN is present, which indicates an increased risk of preterm labor; your doctor will likely have you stay overnight in the hospital to be monitored for uterine contractions. A negative result means that fFN isn’t present, and you’ll likely be pregnant for at least another week, at which point your doctor might check you again.